Yoon Hyung Hur

Topographically-designed triboelectric nanogenerator via block copolymer self-assembly.

Herein, we report a facile and robust route to nanoscale tunable triboelectric energy harvesters realized by the formation of highly functional and controllable nanostructures via block copolymer (BCP) self-assembly. Our strategy is based on the incorporation of various silica nanostructures derived from the self-assembly of BCPs to enhance the characteristics of triboelectric nanogenerators (TENGs) by modulating the contact-surface area and the frictional force. Our simulation data also confirm that the nanoarchitectured morphologies are effective for triboelectric generation.

Proximity Injection of Plasticizing Molecules to Self-Assembling Polymers for Large-Area, Ultrafast Nanopatterning in the Sub-10-nm Regime

While the uses of block copolymers (BCPs) with a high Flory-Huggins interaction parameter (χ) are advantageous for the improvement of resolution and line edge fluctuations of self-assembled nanoscale patterns, their slow chain diffusion results in a prolonged assembly time. Although solvent vapor annealing has shown great effectiveness in promoting the self-assembly of such BCPs, a practical methodology to achieve a uniform swelling level in wafer-scale BCP thin films has not been reported. Here, we show that a solvent-swollen polymer gel pad can be used as a highly controllable vapor source for the rapid, large-area (>200 mm in diameter) formation of sub-10-nm patterns from a high-χ BCP. The proximal injection of solvent vapors to BCP films and the systematic control of the swelling levels and temperatures can significantly boost the self-assembly kinetics, realizing the formation of well-aligned sub-10-nm half-pitch patterns within 1 min of self-assembly. Moreover, we show that the gel pad can be used for the shear-induced alignment of BCP microdomains in an extremely short time of ~5 s as well as for the generation of three-dimensional crossed-wire nanostructures with controlled alignment angles.

High-resolution nanotransfer printing applicable to diverse surfaces via interface-targeted adhesion switching.

Nanotransfer printing technology offers outstanding simplicity and throughput in the fabrication of transistors, metamaterials, epidermal sensors and other emerging devices. Nevertheless, the development of a large-area sub-50 nm nanotransfer printing process has been hindered by fundamental reliability issues in the replication of high-resolution templates and in the release of generated nanostructures. Here we present a solvent-assisted nanotransfer printing technique based on high-fidelity replication of sub-20 nm patterns using a dual-functional bilayer polymer thin film. For uniform and fast release of nanostructures on diverse receiver surfaces, interface-specific adhesion control is realized by employing a polydimethylsiloxane gel pad as a solvent-emitting transfer medium, providing unusual printing capability even on biological surfaces such as human skin and fruit peels. Based on this principle, we also demonstrate reliable printing of high-density metallic nanostructures for non-destructive and rapid surface-enhanced Raman spectroscopy analyses and for hydrogen detection sensors with excellent responsiveness.

Host-Guest Self-assembly in Block Copolymer Blends

Ultrafine, uniform nanostructures with excellent functionalities can be formed by self-assembly of block copolymer (BCP) thin films. However, extension of their geometric variability is not straightforward due to their limited thin film morphologies. Here, we report that unusual and spontaneous positioning between host and guest BCP microdomains, even in the absence of H-bond linkages, can create hybridized morphologies that cannot be formed from a neat BCP. Our self-consistent field theory (SCFT) simulation results theoretically support that the precise registration of a spherical BCP microdomain (guest, B-b-C) at the center of a perforated lamellar BCP nanostructure (host, A-b-B) can energetically stabilize the blended morphology. As an exemplary application of the hybrid nanotemplate, a nanoring-type Ge2Sb2Te5 (GST) phase-change memory device with an extremely low switching current is demonstrated. These results suggest the possibility of a new pathway to construct more diverse and complex nanostructures using controlled blending of various BCPs.

Synthesis of poly(styrene-b-4-(tert-butyldimethylsiloxy)styrene) block copolymers and characterization of their self-assembled patterns

Directed self-assembly (DSA) of block copolymers (BCPs) is regarded as one of the alternative methods to traditional top-down lithography approaches due to its ability to form well-aligned nanostructures such as spheres, cylinders, and lamellae with controlled domain size. Despite extensive research activities in this field, the question of how the Flory–Huggins interaction parameter (χ) and polydispersity of chains affect self-assembled pattern formation remains. Here, we report the self-assembly behavior of poly(styrene-b-4-(tert-butyldimethylsiloxy)styrene) (PS-b-P4BDSS) BCP, which has an intermediate χ between those of poly(styrene-b-methyl methacrylate) (PS-b-PMMA) and poly(styrene-b-dimethylsiloxane) (PS-b-PDMS), which allows pattern formation of the BCP in a wide range of length scales induced by simple thermal annealing. We also demonstrate the effect of polydispersity on self-assembled pattern quality by comparing BCPs synthesized via anionic polymerization with those synthesized via reversible addition fragmentation chain transfer (RAFT) polymerization. The self-assembled pattern of BCPs with a narrow PDI (PDI 1.15 via RAFT polymerization).